08/14/09

For work, I've been thinking about ways to easily track the movement of convective cells in radar data. It's easy to define the existence of a convective cell as any area with a reflectivity greater than a certain threshold. If you stack successive radar scans on top of each other you can used what's called connected component labeling to track how convective cells move across a radar domain so long as some part of the cell occupies the same area from one scan to the next. Thus, you can keep track of what happens to a cell as it moves, splits, merges, dies out, etc...

Below is a visualization where I show three radar scans from a collection of scans. Also displayed is a 35 dBZ isosurface that shows how convective cells move and change between the scans displayed. This isn't a methodology and toolkit that I've perfected for research use yet, but the image below represents a good proof-of-concept.

06/21/09

NEC ARTICLE 400 Flexible Cords and Cables General 400.1 Scope.
This article covers general requirements, applications, and construction specifications for flexible cords and flexible cables.
400.8 Uses Not Permitted.
Flexible cords and cables shall not be used for the following:
(1) As a substitute for the fixed wiring of a structure
(2) Where run through holes in walls, structural ceilings, suspended ceilings, dropped ceilings, or floors
(3) Where run through doorways, windows, or similar openings
(4) Where attached to building surfaces
Exception: Flexible cord and cable shall be permitted to be attached to building surfaces in accordance with the provisions of 368.8.
(5) Where concealed by walls, floors, or ceilings or located above suspended or dropped ceilings

What this means is that if the power cord for your wall-mounted TV - or any other appliance for that matter - is run through the wall, you're in violation of the electrical code. What you're supposed to do it have a standard power socket installed behind the TV and coil up the slack in the power cord to keep it out of sight.

In you do run your cord through the wall and there is a fire, even if the cord in question isn't the cause of the fire, your insurance coverage could be invalidated because of the code violation.

06/18/09

I previously posted about the probabilities of successes for dice roll for the old White Wolf World of Darkness role-playing game system. A few years ago White Wolf release a new system for their games set in the World of Darkness.

The new system does not have varying difficulties. Instead the difficulty of all rolls are fixed at 8. The variable in the new system is the number of dice you throw for a given action: the size of your dice pool. Rolls of one no longer cancel out successes. Also, you only botch when you roll a one with a dice pool of one.

The chart below shows the success probabilities for the new system.

Everything should be pretty self explanatory. For a dice pool of 1, the probability for 0 successes also includes the probability to botch. If the dice pool is one, the botch probability is 10% and can be subtracted from the "0 successes" probability value (70%) if you're interested in the chance to get zero successes without botching (60%).

All stats are based on 1 million simulated rolls for each dice pool size. 10s are re-rolled as per the rules. An 8 or better is considered a successes. MATLAB was used for all calculations.

The next figure is the percent distribution of successes for each of the dice pool sizes. While the figure above shows the cumulative probability of meeting or surpassing a certain success threshold, this figure shows the actual distribution of successes rolled and gives you a better idea of what a roll of a certain dice pool size will produce.

06/08/09

I'd like to congratulate the VORTEX 2 research teams. They finally managed to collect some data on tornado producing super cells. There is only a week left in the project and a lot of people where worried that they would go the whole project without observing a single tornado.

05/05/09

Many of my co-workers here at NCSU left this week to participate in the VORTEX 2 field research project in the Great Plains. The purpose of VORTEX 2 is to study the formation of tornadoes. VORTEX 2 involves hundreds of researchers from dozens of universities and labs. The NCSU research team consists of 5 graduate students and Dr. Matthew Parker. You can follow the blogs of the NCSU vortex participants via the following links: